Astronomy Without A Telescope – Our Ageing Universe


It all started so full of promise. All at once, our universe burst upon the scene, but much of that initial burst quickly dissipated into background neutrinos and photons – and ever since, pretty much  everything our universe has ever done has just dissipated more energy. So, despite the occasional enthusiastic outburst of supernovae and other celestial extravagances, it’s becoming increasingly apparent that our universe is getting on a bit.

The second law of thermodynamics (the one about entropy) demands that everything goes to pot over time – since anything that happens is an opportunity for energy to be dissipated.

The universe is full of energy and should always remain so, but that energy can only make something interesting happen if there is a degree of thermal disequilibrium. For example, if you take an egg out of the refrigerator and drop it in boiling water, it cooks. A useful and worthwhile activity, even if not a very efficient one – since lots of heat from the stove just dissipates into the kitchen, rather than being retained for the cooking of more eggs.

But, on the other hand, if you drop an already cooked, already heated egg into the same boiling water… well, what’s the point? No useful work is done, nothing of note really happens.

This is roughly the idea behind increasing entropy. Everything of note that happens in the universe involves a transfer of energy and at each such transfer some energy is lost from that system. So, following the second law to its logical conclusion, you eventually end up with a universe in thermal equilibrium with itself. At that point, there are no disequilibrium gradients left to drive energy transfer – or to cook eggs. Essentially, nothing else of note will ever happen again – a state known as heat death.

It’s true that the early universe was initially in thermal equilibrium, but there was also lots of gravitational potential energy. So, matter (both light and dark) ‘clumped’ – creating lots of thermal disequilibrium – and from there all sorts of interesting things were able to happen. But gravity’s ability to contribute useful work to the universe also has its limits.

In a static universe the end point of all this clumping is a collection of black holes – considered to be objects in a state of high entropy, since whatever they contain no longer engages in energy transfer. It just sits there – and, apart from some whispers of Hawking radiation, will just keep sitting there until eventually (in a googol or so years) the black holes evaporate.

The contents of an expanding universe may never achieve a state of maximum entropy since the expansion itself increases the value of maximum entropy for that universe – but you still end up with not much more than a collection of isolated and ageing white dwarfs – which eventually fizzle out and evaporate themselves.

A head count of the contributors to entropy in our universe. Supermassive black holes top the list. Credit: Egan and Lineweaver. (The full paper notes some caveats and recommendations for further work to improve these estimates).

It’s possible to estimate the current entropy of our universe by tallying up its various components – which have varying levels of entropy density. At the top of the scale are black holes – and at the bottom are luminous stars. These stars appear to be locally enthalpic – where for example, the Sun heats the Earth enabling all sorts of interesting things to happen here. But it’s a time-limited process and what the Sun mostly does is to radiate energy away into empty space.

Egan and Lineweaver have recently re-calculated the current entropy of the observable universe – and gained a value that is an order of magnitude higher than previous estimates (albeit we are talking 1×10104 – instead of 1×10103). This is largely the result of incorporating the entropy contributed by recently recognized supermassive black holes – where the entropy of a black hole is proportional to its size.

So this suggests our universe is a bit further down the track towards heat death than we had previously thought. Enjoy it while you can.

Further reading: Egan, C.A. and Lineweaver, C.H. (2010) A Larger Estimate of the Entropy of the Universe

35 Replies to “Astronomy Without A Telescope – Our Ageing Universe”

  1. Oh, please. Most we always anthropomorphize? We have no idea of whether the universe is young, middle-age, or old. We believe that we have a good estimate of the present age and maybe the size but again, in John Cage fashion, I ask, PLEAZE!

    Compare the life of the universe to the life of a person when there are infinite possiblities over the next trillion years is…

    Please stop. That is not science.

  2. Like many readers of this page, I frequently find Mr. Nerlich’s comments very humorous and appreciate them. But here, I am glad that he didn’t try to boil the chicken in order to get at the egg~ Allow me….

    What about White Holes? They too were part of Einstein’s thinking when he postulated Black Holes. But, since that might bring up all sorts of unpleasant implications, like multiverse theory, worm hole theory or even Plasma Universe theory, we’d better best go along with the accepted numbers and equations, no matter how absurd those quesstimations appear to be…

  3. Wow picky crowd tonight!

    I’d hardly call young, middle, old age’ed ness an anthropomorphism. More like a life-o-pomorphism as those terms of age can best be applied to living things, not just humans.

    As for white holes … apparently they are possible in theory, but they become unstable and vanish the moment they interact with anything at all … a single photon from the cosmic microwave background is enough to do it. Explain how all your unpleasant implications can work under such circumstances Aqua. … oh right, nevermind, you cant.

  4. Interesting clicking on Lineweaver’s name on the Arxiv page. He seems to make a specialty of these ‘big-picture’ comparisons and surveys.

    It’s something we could do with more of, though I didn’t like the way the ‘potato radius’ work was presented across the internet as something new and startling, when it effectively repeated what was being said widely a few years previously.

  5. I always think explaining the heat death by entropy to be overly simplistic. Despite the pluralistic interpretation of the law of thermodynamics, we still dont know how gravity works and cant identify what most of the universe is made from. I think that on that basis its fair to keep an open mind about this interpretation.

    One pertinent outcome of a this future state of equilibrium might be very very massive black holes that spawn child universes.

    Sean Carroll does a good talk about this. (Mostly in part2)


  6. @Aqua:

    “What about White Holes? They too were part of Einstein’s thinking when he postulated Black Holes. But, since that might bring up all sorts of unpleasant implications, like multiverse theory, worm hole theory or even Plasma Universe theory, we’d better best go along with the accepted numbers and equations, no matter how absurd those quesstimations appear to be…”

    What about green cheese?

  7. Thanks all for comments. It’s a good day when the first one in isn’t pointing out multiple typos.

    @ damian
    Agree there’s plenty of unknowns in this space 🙂

    In the general context you put forward, I’ll suggest there’s a big problem with dark energy. If it’s essentially ‘free’ energy – then it’s appearance out of nowhere is in clear conflict with the second law.

  8. I hope nobody with depression reads this article – whilst I appreciate the intent it rather portrays the entire universe as pointless (OK that is anthropomorphism too but…) Add in the idea of proton decay and you could get really down 😉

  9. On a philosophical level There is an (antitheses) to the age old example of the Broken Egg analogy often used to describe Entropy.

    i.e: Once the egg is broken there is no way to put it back together again.

    That is true in the (one) instance of that specific egg. However nobody ever seems to mention that there are lots of chickens still around to make more eggs.

    Perhaps what is missing in the equations is the inclusion of systems (aka the chicken) that re-integrate disorder and recycle it.

    We see renewal of transmuted energy all around us, very efficient systems that always adapt to the energy available. If the universe if halfway in its life then the preponderance of Brown Dwarf stars is a good sign of increasing efficiency in the universe.

    Increasing efficiency can also be an analog for increasing complexity. So while on one hand the arrow of time is increasing entropy Im not necessarily convinced that the final outcome is going to be without disequilibrium gradients.

    Not as long as systems exist that recycle entropy.

    If we find that there is a geometry and ordered structure in the spin of nuclei around atoms that defines gravity rather then a singular particle such as the Higgs boson (aka top Quark) then that might open a whole new line of reasoning on this subject. Perhaps we would then have to account for how energy is ordered not only its existence in absolute numbers.

    Pure (layman’s) conjecture on my part, please take it as such. 🙂 I know my understanding of these issues is limited.


    P.S> Also of interest might be this paper by Nikodem J. Poplawski suggesting our universe may exist in a Black hole.

  10. Thanks for yet another very interesting article. I’m very much a starter in trying to come to come to grips with all this facinating stuff.

    I wondered about one thing you wrote:

    “you still end up with not much more than a collection of isolated and ageing white dwarfs – which eventually fizzle out and evaporate themselves”.

    I thought these just sat there and got colder and colder. What is the mechanism responsible for their ultimate demise and evaporation?

  11. @damian:

    “Perhaps what is missing in the equations is the inclusion of systems (aka the chicken) that re-integrate disorder and recycle it”

    That’s when it really starts to become interesting, although at this time is only at speculation level….

    Well said!

  12. White holes, eggs & chickens etc. Some interesting questions.

    Life on Earth appears to violate a whole lot of thermodynamics. Even the appearance of a tree might be puzzling in a way, for most of its mass we observe is high above the ground, making it out of equilibrium. Yet the Earth is an open thermodynamic system, which is a tiny system driven by a closed thermodynamic system called the sun. The sun is a closed system which generates energy that is largely heat (black body radiation spectrum of maximal disorder) which is dumped into the environment, which is open space. For Earth there is then this heat input which can run through the planetary system before that energy is dumped into the cold blath or environment of cold space at a higher entropy than we received it. So there continues to be photosynthesis by plants, plants get eaten on by insects, which in turn are eaten by birds and bird eat seeds. So if you break an egg you will get it replaced, just as there is entropy in death, but there is birth as well. In fact my daughter was born the same day my grandmother died, making for some interesting family dynamics.

    As for white holes, these can be seen in a couple of ways. These emerge from a conformal realization of the Schwarzschild metric for black holes. There is time symmetry between two spacelike regions with a singularity that have event horizons bounding a timelike region (actually two of them) that is our universe. Geodesics of matter and radiation from one spacelike region are outgoing and the other has ingoing geodesics. These define the white hole and black hole respectively. Now this is an exact solution result of the Einstein field equations, an eternal black hole, so we don’t expect every black hole to have a corresponding white hole. Generally the conformal theory or Penrose diagram is truncated off so the black hole is not an idealized eternal system and is instead the result of mass-energy imploding into a small region of space. In this physical sense the white hole is removed. However, white holes return in a way in inflationary cosmology.

    Inflationary cosmology is an early phase of the universe where the scale factor for space exponentially expanded. The FLRW dynamical equation is

    (a’/a)^2 = q rho,

    a’ = time derivative of the scale factor, q = constant (8piG/3), and rho the density of mass-energy. During inflationary period this density is about constant in time (not exactly though) and the differential equation gives the scale factor with time as a = exp(sqrt{L/3}t), where L is the “Lambda” for the cosmological constant. During the inflationary phase of the universe this Lambda was 10^{120} times larger than it is today. So the universe went through a period in its first 10^{-20} seconds of existence exponentially expanding very rapidly. Now if the universe had any inhomogeneous distribution of mass-energy and spacetime curvature prior to inflation these were stretched out enormously as spacetime was flattened out. So inflation did a sort of dry cleaning job on any bunching up or ripples in the earliest universe, and starch pressed spacetime into a flat surface. So let us look at the process in reverse time. The universe would be exponentially shrinking and asymptotically slowing down until the wrinkles begin to appear. As the wrinkles appear these clumps could focus inwards to form black holes. But wait a minute! We are looking at black holes in reverse time, which in ordinary forward directed time are white holes! So these white holes appear to result from instantons (self-dual tunneling quanta fluctuating through a “barrier”) which generated our observable universe.

    The forwards direction of time is a bit of a puzzle, and why the universe was generated with such low entropy appears puzzling as well. The universe emerged with remarkably low entropy, which is not in equilibrium with how it is configured today. Further, the entropy of the universe today is not at equilibrium with how it will appear in 10^{50} years, where regions bounded by the cosmological horizon can contain a supermassive black hole. This configuration is also not in equilibrium with the universe in 10^{100} years where these black holes will have quantum mechanically decayed by Hawking radiation. At this time the universe is a de Sitter spacetime vacuum, but even this is not an equilibrium configuration, for the horizon defining the de Sitter vacuum decays and expands off “to infinity” over a near infinite time period. Tthis Hawking-Gibbon radiation decay means the universe as time “goes to infinity” approaches a pure Minkowski spacetime or perfect void of nothing.

    There are a number of ways this might be seen. Suppose the universe quantum resulted from the quantum tunneling of a “blob” of mass-energy from some other cosmology. This is that instanton mentioned above. This blob is a 3 dimensional sphere of space far smaller than a nucleus. The number of Planck units of space this contains is fairly small. So the entropy bound is by the Khinchin-Shannon theorem very small as well, but it is maximal for the scale of that blob. However, the thermodynamics of spacetime physics is strange. It does not approach equilibrium in the standard way. This is seen with Hawking radiation of a black hole. Consider a black hole with mass M and a temperature T ~ c/T, c = constant, in a universe with a background radiation of the same temperature T. If the black hole quantum radiates a bit of mass-energy its mass reduces and it temperature increases. It is then hotter than the background as statistically it is more favorable for it to quantum radiate away. Conversely, if the black hole absorbs a unit of mass-energy from the background it is colder, where now it is statistically likely to begin to absorb mass-energy from the background and grow. So equilibrium does not exist in the same way it does with standard thermodynamics. The heat capacity of spacetime is negative, which is one way to look at it.

    As a result that blob which emerged by a quantum fluctuation will inflate away so its entropy will always increase, as with the inflationary phase of the universe. There are a lot of unknowns here. In particular we don’t have a handle on the physics of that instanton or “blob,” and a quantum gravity which tells us how that emerged in an explicit way. Further, the de Sitter spacetime configuration of the universe, such as during the early inflationary period, is not a perfect exponential expansion. The expansion of the scale factor obeys a cosh function a = cosh(sqrt{L/3}t), which for large t is about exponential, but for small t turns around in a way. So there is something similar to the white hole with de Sitter cosmology. This may be involved with the tunneling process and the nature of this instanton. However, brevity and time prevent me from pursuing that matter further here — even if it is a fascinating thing to work on and discuss!

    The universe is in this stellar phase, which in light of the possible future of the universe is a down right babe in arms phase. The universe will exponentially expand in this latent de Sitter phase, only to get colder and darker with time. The fate of any intelligent life is sealed, or doomed, for some people have pondered how long any intelligent life might be able to survive into the future. The upshot is that available matter-energy will always run away from you faster than you can acquire it. So we are doomed — hurray! However, this is a sort of ultimate doom very far into the future and has little to do with our parochial problems we have foolishly generated here on Earth.


  13. Protons should decay with a the half life is about 10^{34}-10^{36} years. The decay occurs because any quark can transform into a lepton. So given a quark, call it q there are gauge rotations, or gauge particles, such that q + X – -> l = lepton. At high energy these processes occur all the time, but at low energy the large effective mass of these gauge particles means it requires an unusually large quantum fluctuation of energy to generate this X-particle. In 10^{40} year protons will have largely decayed away, and the tiny percentage remaining will have been exponentially dispersed away from each other.

    The object which earns the award for longevity is the neutron star. These may exist for up to 10^{200} years. If there is no proton decay then neutron stars may exist for up to 10^[10^{76}} years, which is the time for a quantum fluctuation to convert a neutron star into a black hole.

    The universe is going to be dark and cold, and remain that way for essentially eternity.


  14. @Surak: Your statement “Explain how all your unpleasant implications can work under such circumstances Aqua. …”

    I find that it is “unpleasant” to question currently accepted theory(s). Those who champion one explanation or another for the formation and existence of our universe, although using the best currently available information, are vehemently predisposed to defend whichever theory they are currently attracted to and/or have studied. I find this to be rather an evolutionary limitation, or a function of our current time line. It is almost certain that in describing the universe with our bicameral minds, we are misled into accepting ‘dead end’ theoretical conclusions. It may be that the ‘real truth’ behind the structure and origin of our universe is beyond us at this point in time, and that there is a reason for that. Simply put.. we are not ready to accept the infinite with finite minds.

    I do however believe that we are on the brink of an evolutionary ‘breakthrough’… and that all things shall be revealed, when we are able to open ourselves up to infinite possibility. i.e. There are more answers than questions. Remember… time is a subset of our illusions.

    “Be Thee reborn, with the renewal of Thy mind…”

  15. Sorry about that… its Sunday and I was thinking in terms of SPIRIT instead of science. Sheesh.. I wish I could formulate THAT in reasonable numberszuh? How about 1 + infinity = I AM? LOL… and withdraws with a sheepish grin.

  16. The analogy of the boiled egg is not exact. You can say that most of the energy is dissipated. But in reality the energy is making work, heating the environment. In galatic dimensions what happens to the energy radiatiated by the stars ? The energy is not lost, it is within the universe. The problem is that we don’t know what happens to the energy after it is radiated. This also applies to Hawking radiation .

  17. @Nedim Ardoga
    Thanks for your comments, I feel I should respond:

    The analogy of the boiled egg is not exact.
    – Agreed, it’s an analogy.

    You can say that most of the energy is dissipated.
    – I said a bit of it was dissipated, albeit eventually it’s all dissipated.

    But in reality the energy is making work, heating the environment

    – To pull all this together… The bit of energy that is dissipated is not lost – it heats the rest of the universe. But that just means raising the mean background temperature of the universe to an infinitesimal level above its current temperature of 2.7 Kelvin.

    The outcome of all this is just regression to the mean background temperature of the universe.

  18. The bit of energy you said which heated the Universe is not a total loss. The Universe will quickly cool back to its original temperature.However, some molecules used to create the heat energy were not burned, and likely were tossed out into space. They did not suffer the 3rd law of thermodynamics, but rode along the 2nd law!

    Along these lines the theory remains…
    Unless we find out some odd phenomena is somehow creating and pumping out more hydrogen, eventually all the gas in the Universe will be used up. Stars will eventually fizzle out, blackholes will evaporate, and any other elements left will eventually decay (for all you thermodynamic fans).

    …or perhaps the expansion of the Universe will spin out of control, ripping all atoms and particles apart… sending them to a new dimension to begin another Universe.

    …and then there is green cheese.

  19. As Steve Nerlich says all the energy is dissipated in the end. Boiling an egg increases the energy of the egg and performs work in denaturing peptides in the egg. This denaturing is what gives rise to a hard boiled egg that can be eaten conveniently. After this is done the energy continues to diffuse away as heat, warming up the environment slightly. If the environment is “infinite,” which is an approximation used in some heat cycle calculations the heat is “lost.” The first law of thernodynamics dE = dW – dQ, for dQ = TdS (temperature times change in entropy), W the work and E the free energy, a cycle produces some work plus some lost energy unavailable to do work — the dQ. The second law in addition says that dS/dt >= 0, so the bound energy TdS increases monotonically. So in burning a fuel in a cylinder with a piston some work is done dW with some entropy production. Now that work is also eventually lost as well, say when you apply the brakes on the car to dissipate that kinetic energy into heat.

    When it comes to heating up the universe, things get a bit strange. I indicated above that the mass of a black hole is inversely proportional to the temperature or T = c/M. BTW, I mistyped on this and wrote T = c/T instead. The heat capacity of spacetime, in particular that associated with event horizons, is negative. So if you keep dumping mass-energy onto a black hole the mass of the black hole increases and the event horizon area increases, which correlates with a lowering of the black hole temperature. It is opposite of what you might expect. The universe also has a cosmological event horizon which is similar. So if you try to heat up the universe by throwing out lots of energy or heat you can only at best actually cool it down a bit! That is why those odd popIII stars blew out lots of X-ray, UV and some optical energy failed to heat up the universe, even though they reionized atoms in the universe. One way to think of it is that by pumping radiation into the universe you speed up the diffusive expansion of mass-energy of the universe, which in turn lowers the temperature. The entropy of a black hole is S = A/4L_p^2, for L_p the Planck unit of length L_p = sqrt{G-hbar/c^3} ~ 10^{-33}cm. The area of the black hole, A = 4-pi r^2, for r ~ mass, increases with mass. As a result lower temperature with spacetime physics corresponds to higher entropy —- again opposite of what one normally expects.

    Thermodynamics is a harsh reality, but then again without it we would not exist. In fact the world would not at all resemble what it does. It is a Janus-like blessing and a curse at the same time. The universe will die out, stars will die, protons will decay, the universe will get cold and dark, black hole evaporate and so forth. Thermodynamics is an aspect of our local problems on Earth as well, for we are using up this planet’s natural stocks of free energy far more rapidly than they are replenished by open natural systems.


  20. No one ever seems to remember that Nature always, ALWAYS -!!! recycles everything. So why not (in a trillion years or so) wouldn’t a BRANE bump into another BRANE and start this lovely Big Bang EXPANSION (not explosion) mess all over again? At least that way explains what banged and how it banged and does away with the Guth Inflation crap (just a huge Fudge factor – Which by the way is a 21st century version of Einsteins Cosmological Constant.)
    Maybe the scientists in the next round of Big Bang will get it right and stop moaning about all the DEATH to the Universe crap. Everything doesn’t have to have a bad ending. That is just the current populations mentality or lack of imagination. And the MEMBRANE theory is just as un-proveable as all the crap everybody has been preaching for the past 100 years….

  21. Rudeyd, actually a bump with another brane could happen right now. We would not see a brane coming until it hits us. Far more cooler than a striking meteor.

  22. A question for you guys.
    In a trillion years the energy of the universe will flatten out just like there would be nothing.

    Could it be that something happens that attracts all this energy to one single point and thus starts a second big bang? Maybe a gravitational wave from another nearby universe that manages space-time to shrink into a single dot.

    Did the universe start from a single point indeed so no before existed? Or could it have been collapsed to a sphere that looked like a point before it started to expand again indicating space and time already existed.

  23. I have avoided D-branes in this discussion, largely because the topic is rather strange. The Steinhardt theory introduced the idea that D3-branes oscillate and collide with each other. The “D” here refers to Dirichlet boundary conditions on strings attached to the branes. The strings connect between different branes, sort of like springs connecting the top and bottom of a mattress. In fact there can be a whole stack of Dp-branes so attached, for = dimension of the brane. The strings vibrate and stretch and the branes oscillate with respect to each other. When the D3-branes collide they excite string states on each other and this is associated with a big bang. The string, type I and II string with open ends fixed onto the branes energetically move apart and diffuse away to zero energy density. By the time the two brane collide again the cosmology associated with either one is “dead,” such as a de Sitter vacuum or Minkowski flat spacetime.

    This is a sort of toy model. The strings which attach the branes together can just be vacuum states, so the physics involved is a Casimir effect. The vacuum between the branes is then the quantum barrier an instanton must tunnel across to generate a cosmology. The full cycle between collisions of two D3-branes might represent an infinite time for a cosmology on the each D3-brane. The problem is that we really do not have a good handle on this. How the Dp-brane theoretical perspective fits with the more standard spacetime inflationary perspective on cosmology is not well understood. There is a deep intellectual challenge involved as well. String/M-theory is a vast subject, and it is very difficult to keep up with it all. Further, not all of it can be right —- there is too much there, or too much for our particular spacetime cosmology. There is this other perspective on quantum gravity called Loop Quantum Gravity (LQG), and related ideas with causal triangulations, causal nets and so forth. This approach is more directly related to general relativity, and because of that it can’t all be wrong. Further, these theory involve constraints, which I think may be useful in restricting the variables or degree of freedom in the string/M-theory. Yet getting these two theoretical understanding to work together is infernally tough. Further, the two communities (strings and LQG) of physicists are intellectually rather hostile to each other. Trying to get people on both sides of the fence to read and listen to something which might connect the two is very tough.

    So this is in many ways where the fun lies, but it is also tough.


  24. Oh dear me! I’m away a few days in the wilderness (read: home town) and look what happens in civilization (read: internet).

    Maybe I can field some outstanding points to start with:

    @ Buxtehude:

    I think that would be if nucleons (protons, neutrons) are decaying. With todays observations, this doesn’t seem to happen. IMO the article got a little ad hoc at this point.

  25. @ Olaf:

    In a trillion years the energy of the universe will flatten out just like there would be nothing.

    It is globally flat today, see standard cosmology.

    But that was a lead in for your question about cycling universes. I believe some people have come up with problems, perhaps explicit as regards brane recycling universes in string theory (“ekpyrotic cyclic universes”) as they seem to be out, but more importantly general problems. The later may have been Boussou among others in fact, but my memory on this is vague. You will have to check.

    Did the universe start from a single point indeed so no before existed?

    In chaotic inflation, and perhaps hybrid inflation, spacetime will inflate so massively [sic!] that the observable universe AFAIU could have originated in a Planck volume.

    Of course the parsimonous theory is that the universe is infinite in extent. But it may be that a model as the one you suggest makes predictions that allow us to conclude that a single Planck volume was the originating system.

    In any case, since universes are zero energy (and I’m not going to reference that paper again unless asked; it’s on arxiv), they can tunnel from preexisting universes. But your idea reminds me of the description of Vic Stenger in “GOD – The Failed Hypotheses” of how something can naturally spontaneously symmetry break out of the ultimate symmetry of nothing (chaos).

  26. @ LBC:

    I have a vague feeling that I’ve dropped a similar thread before vacation (but I’m saving all links so intend to get to it eventually), so with excuses:

    Further, not all of it can be right —- there is too much there, or too much for our particular spacetime cosmology.

    That is why these theories are naturally amenable for environmental selection. It is precisely analogous to field theory which all of it can not be right for a particular problem: boundary conditions sets the field and a free bias potential.

    So this is not a problem, it is a feature.

    This approach is more directly related to general relativity, and because of that it can’t all be wrong.

    But this argument is all wrong.

    Since GR is an effective theory, this is exactly like having a map and then claiming that understanding how to make paper and ink makes you understand how the terrain developed.

    [With more excuses, because this isn’t an straight arrowed argument but perhaps an analysis of sorts, one can make this into a joke between loop quantum gravity and string theory guys. This was a type of “argumentation” that was so popular a decade ago, but it is still illustrative to newcomers:

    Two guys want to build a house, but have no idea how.

    Day 0:

    [LQG] – So I have this house drawing. Maybe if I cut it in small pieces, I can use them to build with.

    [ST] – I have never build a house before. But I have this wonderful material I found after some initial experimenting, gravel. I can do most anything with it, even cement it to bricks and build roads and bridges.

    Maybe I should try to build that house. Where is that drawing?

    Day 2:

    [LQG, giving up trying to fold paper bits into a semblance of a house but not making a sturdy block even, goes over and watch ST]:

    – Hey! You are using a brick scaffolding to hold your walls up! That is cheating, the finished house has nothing like it. See here in the drawing.

    [ST shakes head, and continues to put a block on top of the wall.]

    – There, it is starting to look like a house. Wonder if I can put more windows in without it crumbling when the scaffold goes off?

    [ST does so, looks on when the whole work shakes and fall]

    – Too many windows. Oh well, eventually I will get it right. At least I have shown the bricks can build house walls.

    Now where should I put that first brick again? *starts building anew*]

  27. light cannot escape from inside any size of black hole,in fact it disappears inside atomic black holes. It’s far premature to declare a death to the universe, when what we see could be energy visible matter coming out of quantum flat white holes. The 2nd law of thermodynamics is really about irreversibility. Wormholes of tiny mass are very brief to us outside its horizon, but would last very long if our mass and size was reduced to that of a photon we could observe it. Eventually the mini-black hole would evaporate explode like the big-bang. Timescales we create and think that a picosecond is very brief yet if we had a telescope that could capture picosecond light we would see so much more of the universe that we all would be utter fools today.

  28. Attempting to figure out how the universe emerged form a single Planck volume is not possible, at least not as we can understand things. The problem is that a Planck unit can only carry at most one quantum bit of information. The entropy S = -k*n*log_2(n) = 0 for n = 1. We have no information to work with.

    Torbjorn Larsson OM: There is some sort of “selection,” which Smolin and others have compared to a Darwinian process. So each 4 dimensional spacetime cosmology in the grand superspace of 26 dimensions exhibits structure which is selected by some mechanism. This mechanism is related to a post-selection process on quantum states or quantum trajectories. Seth Lloyd has written recently an article on this with connection to closed timelike trajectories

    and I think this is in a holographic setting involved with how certain spacetime cosmologies (universes in the so called multi-verse) are realized. This paper by Lloyd might make an interesting topic here at UT. It involves how one can have time travel in a quantum mechanical sense without the causal paradoxes of time travel, such as the “McFly problem” in the movie “Back to the Future.”

    I think aspects of that selection process are the constraints in LQG. This is closely tied to Einstein general relativity, which admittedly is an effective theory. However, it is still not all wrong — it is just not all correct. One problem with the LQG approach is the Barbero-Immirzi ambiguity which leaves a black hole entropy S = 3A/16L_p^2 instead of S = A/4L_p^2, which is correct. There is also twistor theory as well, which might play some role in this fusion.


  29. As I indicated above if one rewinds the clock of time with inflation, which flattened and smoothed out the wrinkles (gravity waves and gravitons) in spacetime, then very near the initial quantum process the clumping under this time reversal would form black holes. Now flip the arrow of time in the actual direction of time and you have white holes. There is one thing to consider. These existed in the first 10^{30} seconds or so of the universe, well before the sphere of last photon scatter which is the CMB. Consequently the quanta emitted by these white holes, gravitons, are enormously redshifted. The redshift factor is in fact around z ~ 10^{50} or so. So these very short wavelength gravitons have been smoothed out and stretched into very long wavelength gravity waves. In fact these waves are so long they are as long as the optical limit of the universe itself. They will have left an imprint on the CMB in what are called B-modes. The Planck spacecraft is searching for them right now.

    The further back into the evolution of the universe you try to probe the longer is the redshifting of quanta involved and the weaker their interactions. After graviton production there was the production of neutrinos, which are notoriously weakly interacting. So if we were clever enough we might be able to image an early phase of the universe with neutrinos. It might just be that clumps of dark matter are such an image. Dark matter is a condensate state of the supersymmetric pairs of the Higgs, neutrino and the Z particle. Under supersymmetry rotation these all have the same quantum number. So it might well be that the distribution of dark matter is a “freeze frame” image of particle interaction in the most early universe.

    Wormholes are another matter, and this gets into some subtle issues of quantum gravity. These don’t likely exist as macroscopic objects. They can be converted into time machines.


  30. Wow, you guys never respond to a thread that old….. I owe an apology to you mega minds out there. But I have written several big names and didn’t really expect any response, I was simply venting for the sake of my own brain cell. (on this subject, seldom plural).
    I just have always had a real issue with the Universe before the Bang. “Out of nothing” makes zero sense to me. The mega-brains say that information can never be destroyed or lost permanently, so how can you get something from nothing? We are ourselves recycled along with all things, so why not the Universe itself? Also, I was taught that the BB was an enormous and instantaneous expansion of space into existence – not an explosion. It seems I only began hearing everyone call it an explosion since the inflation theory came around, which lead me to think in completely different ways about what WAS available at plank time point .gazillion zero one.
    True an explosion wouldn’t be an equal distribution of anything like the CMB shows – but just for a moment…. consider the BB as just a “straight up” expansion instead – caused by a brane bump or whatever you believe MIGHT have caused it. An expansion wouldn’t be messy like an explosion. You can get bazillion degree heat without an explosion……You wouldn’t need the Universe to stop, get equal and then “magically” inflate or what not. The fact that the CMB needs anything of the sort kind of irks me because it seems so beautiful on it’s own. Now they are finding more “dark” stuff that we don’t understand so I suppose there will be a “new” CMB theory soon. “Dark Flow”??? C’mon.. REALLY??
    When did the science of Space and Cosmology become such a commercialized entity any way? I guess that is what irritates me the most, everybody is so bent on the Nobel prize these days that we now need band aids and fudge factors for everything.

    Aren’t we over thinking the beauty of some of this a tad too much?

  31. @ rudeyd

    “Out of nothing” makes zero sense to me.

    Yup, very logically indeed but this is what is actually measured. The universe does clearly not follow human logic. So human logic is either not good enough to understand the universe or the human logic flawed.

    “True an explosion wouldn’t be an equal distribution of anything like the CMB shows”

    The big bang is in no way related to an chemical explosion. You are assuming that heat expands the universe which is not true.

  32. The question of whether the universe emerged from nothing, or whether it quantum tunneled from some other universe, say a cosmology which exist in some superspace or “multiverse,” is not well understood. The universe may be a 26 dimensional superspace, from the 26 dimensional bosonic string theory with 26 = 10 + 16 dimensions of supergravity and the heterotic string space, where spacetime cosmologies are 4 dimensional supespaces. These may be connected to each other by quantum mechanical processes. This may involve vacuum energy tunneling between them to form nascent or baby cosmologies, or it may involve D-brane collisions with open strings connecting them and so forth. The two perspectives might in some ways be equivalent.

    The big bang is an expansion of the space of the universe, and not the explosion of matter and energy in space. The “blob” of vacuum which tunneled across a barrier to generate this universe had an enormous energy density. We can think of the evolution of the universe as a process where by the space of the cosmos expands in response.


  33. So OK – maybe our universe is the result of some bizarre quantum rebound that occurred in a parallel universe.

    But that just raises two key questions:
    1) Really? Are we really the result of a quantum rebound in a parallel universe? How do we test that hypothesis; and
    2) So OK, how did that parallel universe come about?

    If we refer the universe problem to another universe, fine – but then let’s deal with the issue of how that other primeval universe came to be.

    Otherwise, it’s just turtles all the way down 🙂

  34. I will try to keep this to some brevity. First off the thread here is trending off to the archive pages here at UT, the other is that my time is a bit limited. Are things (life the universe and everything, turtles all the way down? Maybe, yet whether it this is the case or not the situation is such that we can’t possibly know it all. There are empirical and theoretical reasons for this.

    There are four levels of cosmology. The first two of these we might have some chance of empirically testing and understanding scientifically. The other two levels are far less likely to ever by confirmed. I just mention these briefly, and I have discussed these in some more depth here.

    The first of these is the pocket universe. In previous discussions on inflationary cosmology I mention that our observable universe is a case in the whole space of the universe where the scalar field or inflaton assumes a quadratic form with a very small minimal value. There may be up to 10^{23} of these region in the entire spacetime. So our observable universe exists in a mole of pocket universes.

    The second of these is a deeper universe, which involves a vast number of spacetimes (maybe 10^{500} of these) in a grand superspace. These cosmologies are connected to each other quantum mechanically. The origin of one spacetime according to any observer in that spacetime is connected quantum mechanically to quantum fluctuations with another spacetime cosmology. This is what might be called the spacetime “target” theory from the M-theory string variables which gets into the issue of D-brane banging into each other. So our spacetime cosmology is then oriented along a grand time axis in a 26 dimensional Lorentzian spacetime. So along this time axis some universes or cosmologies are in the + direction, others in the – direction and how you choose this orientation is a matter of convention. This 26 dimensional Lorentzian spacetime (or 27 dimensional anti de Sitter spacetime) has some very deep mathematical structure to it, such as quantum error correction codes and is the automorphism group for something called the monster group.

    The next level is the Many Worlds Interpretation (MWI) branching universe. Within this perspective the whole grand 26 dimensional multi-cosmology in the second level above splits off with every decoherent outcome of a quantum collapse or a reduction of states. So that whole gemish branches off into a myriad number of outcomes. This idea of Deutsche and Tegmark has become very popular of late, and MWI has proven useful in quantum information calculations, but the idea is ineffective. There is no experimental possibility of verifying this interpretation of quantum mechanics or any other.

    The fourth and final level is Max Tegmark’s multistructure idea. The above business, at least the first two and maybe the third, is just one possible structure. In other words mathematics is infinite, and out of that within something called first order logic, there might exist an infinite number of other worlds with entirely different structures or mathematical “languages.” The monster group mentioned above might contain some subset of these, but there might exist something far vaster still. This gets us into deeper speculation.

    This ladder of levels (turtles down the chain) the scale of things becomes extreme. From a cosmology perspective this requires looking at the universe further back towards the quantum event leading to our spacetime cosmology. The quantum signatures of this are enormously redshifted and weakly interacting. Particle physics might help some, for the amplitudes of quantum processes tend to be logarithmic A ~ 1/log(M_p/E), and so we can probe at an energy E many orders of magnitude smaller than the Planck energy and still get signatures of that physics. Of course that requires we be doing physics in a domain where conformal symmetry is at least approximate. That might be above about 1TeV and in the range of the LHC. So we might be able to get some oblique data on the first two levels of cosmology.

    The third one I think is almost impossible, and the fourth is simply to “far out” to even speculate on how this idea could be tested.

    There is another problem here. Tegmark formulated his idea in a way to avoid mathematical undecidability, or Godel’s theorem. Yet this is somewhat artificial. How physical incompleteness is related to mathematical incompleteness is not known at all well. Yet if you cut things off at some point, you do so by burying away this little problem. You can then say that to avoid that problem there is then some even deeper level, which at this point is maybe a self-referential network of states — states with no axiomatic structure. Then what might be beneath that? Well the math-logic guys (and quantum states are logic bits) do work on this!

    The cosmology enterprise is ultimately going to end. Lawrence Krauss has commented on this with respect to our observational limits. Cosmology as a science has managed to take off in the last few decades, and it might continue for another 50 years or so. Ultimately though we will find ourselves faced with questions which can’t be scientifically addressed and the whole business will lapse into philosophy. So at that stage we may only end up with unknown turtles all the way beneath the bit that we can actually know.


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